In the case where hydrogen for fuel cells is produced through reforming of a hydrocarbon fuel (e.g., kerosene, LPG, or city gas), in order to reduce poisoning of a reforming catalyst, the sulfur content of the hydrocarbon fuel must be maintained at a low level of 0.05 ppm or less over a long period of time.
Similar to the above-described case, when propylene or butene is employed as a raw material of a petrochemical product, in order to prevent poisoning of a catalyst, the sulfur content of the propylene or butene must be reduced to 0.05 ppm or less.
LPG contains, in addition to sulfur compounds such as methanethiol and carbonyl sulfide (COS), another class of sulfur compounds that have been added as odorants, such as dimethyl sulfide (DMS), 2-methyl-2-propanethiol, and methyl ethyl sulfide (MES). A variety of adsorbents have been proposed for removing sulfur, through adsorption, from such a fuel gas (e.g., LPG or city gas), and prediction of the service life of such an adsorbent is important for the aforementioned purpose.
As has been known, a sulfur compound is detected on the basis of change in color of a zeolite adsorbent (see, for example, Patent Document 1). However, carbonyl sulfide has conventionally been difficult to detect by color testing.
Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2001-305123